Controller and method for administering and providing on-line handling of deviations in a rotary sterilization process

ABSTRACT

A rotary sterilization system, a controller for use in the rotary sterilization system, and a method performed by the controller are disclosed. The system, controller, and method are used to administer a sterilization process performed on a line of containers and provide on-line handling of a deviation in a scheduled parameter during the process. The containers contain a shelf stable food product that is to be sterilized in the sterilization process. In addition to the controller, the rotary sterilization system includes a rotary sterilizer. The controller controls the rotary sterilizer in performing the sterilization process according to scheduled parameters. When a deviation in a specific one of the scheduled parameters occurs, the controller identifies those of the containers that will in response have a total lethality predicted to be delivered to them during the sterilization process that is less than a predefined target lethality.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates generally to a controller foradministering a rotary sterilization process being performed on line ofcontainers. In particular, it pertains to such a controller that alsoprovides on-line handling of a deviation in a scheduled parameter duringthe process by identifying any containers that will be under processedas a result of the deviation.

BACKGROUND OF THE INVENTION

[0002] A rotary sterilization system is a continuous source processingsystem with intermittent product agitation. This system is widely usedin the canning industry to sterilize a shelf stable food productpackaged in containers. It is used most often for sterilizing a foodproduct that benefits from mechanical agitation of the containers.

[0003] A rotary sterilization system includes a rotary sterilizer thathas one or more cooking shells through which a line of containers {1, .. . , i, . . . , I}_(line) are conveyed. The containers are cooked inthe cooking shell(s) at one or more scheduled cooking retorttemperatures. The containers are then conveyed in line through one ormore cooling shells of the rotary sterilizer. Similar to the cookingshell(s), the containers are cooled in the cooling shell(s) at one ormore scheduled cooling retort temperatures.

[0004] The containers {1, . . . , i, . . . , I}_(line) are conveyedthrough each cooking and cooling shell by spiral tracks and a reel. Thereel has a scheduled reel speed and imparts movement while the spiraltracks provide the direction for the containers to be conveyed throughthe shell. This also provides mechanical agitation of the food productwithin the containers.

[0005] In order for the food product in each container i to becommercially sterilized, a total lethality F_(i) over a total timeinterval [t_(f,i), t_(d,i)] that satisfies a predefined target totallethality F_(targ) must be delivered during the rotary sterilizationprocess to the product cold spot of the container. Here, t_(f,i) andt_(d,i) are the feed and discharge times when the container is fed intoand discharged from the rotary sterilizer. The target total lethality isset by the USDA (U.S. Department of Agriculture), the FDA (Food and DrugAdministration), and/or a suitable food processing authority fordestroying certain microorganisms. The reel speed and the cooking andcooling retort temperatures are then scheduled so that each container iwill receive a scheduled time-temperature treatment that delivers atotal lethality to the container which satisfies the target totallethality.

[0006] As is well known, the lethality F_(i) delivered to the productcold spot of a container i over a particular time interval [t_(m),t_(k)] is given by the lethality equation:F₁ = ∫_(t_(m))^(t_(k))10^((T_(cs)(t)_(s) − T_(REF))/z)t

[0007] where t_(m) and t_(k) are respectively the begin and end times ofthe time interval [t_(m), t_(k)], T_(CS)(t)_(i) is the product cold spottimne-temperature profile for the container, z is the thermalcharacteristic of a particular microorganism to be destroyed in thesterilization process, and T_(REF) is a reference temperature fordestroying the organism. Thus, the total lethality F_(i) delivered tothe product cold spot over the total time interval [t_(f,i), t_(d,i)]due to the scheduled cooking and cooling retort temperatures is given bythis lethality equation, where t_(m)=t_(f,i) and t_(k)=t_(d,i).

[0008] The total time interval [t_(f,i), t_(d,i)] and the product coldspot time-time-temperature profile T_(CS)(t)_(i) must be such that thetotal lethality F_(i) over [t_(f,i), t_(d,i)] satisfies the target totallethality F_(targ). In order to ensure that this occurs, variousmathematical simulation models have been developed for simulating theproduct cold spot time-temnperature profile based on the scheduledretort temperatures. These models include those described in Ball, C. O.and Olson, F. C. W., Sterilization in Food Technology: Theory, Practiceand Calculations, McGraw-Hill Book Company, Inc., 1957; Hayakawa, K.,Experimental Formulas for Accurate Estimation of Transient Temperatureof Food and Their Application to thermal Process Evaluation, FoodTechnology, vol. 24, no. 12, pp. 89 to 99, 1970; Thermobacteriology inFood Processing, Academic Press, New York, 1965; Teixeira, A. A.,Innovative Heat Transfer Models: From Research Lab to On-LineImplementation in Food Processing Automation II, ASAE, p. 177-184, 1992;Lanoiselle, J. L., Candau, Y., and Debray E., Predicting InternalTemperatures of Canned Foods During Thermal Processing Using a LinearRecursive Model, J. Food Sci., Vol. 60, No. 4, 1995; Teixeira, A. A.,Dixon, J. R., Zahradnik, J. W., and Zinsmeister, G. E., ComputerOptimization of Nutrient Retention in Thermal Processing of ConductionHeated Foods, Food Technology, 23:137-142, 1969; Kan-Ichi Hayakawa,Estimating Food Temperatures During Various Processing or HandlingTreatments, J. of Food Science, 36:378-385, 1971; Manson, J. E.,Zahradnik, J. W., and Stumbo, C. R., Evaluation of Lethality andNutrient Retentions of Conduction-Heating Foods in RectangularContainers, Food Technology, 24(11):109-113, 1970; Noronha, J.,Hendrickx, M., Van Loeg, A., and Tobback, P., New Semi-empiricalApproach to Handle Time-Variable Boundary Conditions DuringSterilization of Non-Conductive Heating Foods, J. Food Eng., 24:249-268,1995; and the NumeriCAL model developed by Dr. John Manson of CALWESTTechnologies, licensed to FMC Corporation, and used in FMC Corporation'sLOG-TEC controller.

[0009] However, if any of the actual retort temperatures in the cookingand cooling shells drops below a corresponding scheduled cooking orcooling retort temperature, a temperature deviation occurs.Traditionally, when such a deviation occurs, the controller stops theshells' reels and prevents any of the containers {1, . . . , i, . . . ,I}_(line) from being fed into or discharged from the rotary sterilizeruntil the deviation is cleared. But, this approach causes numerousproblems. For example, significant production down time will result.And, many containers { . . . , i, . . . }_(overpr) will be overprocessed since the total lethalities { . . . , F_(i) over [t_(f,i),t_(d,i)], . . . }_(overpr) actually delivered to their product coldspots will significantly exceed the target total lethality F_(targ). Allof these problems may result in severe economic loss to the operator ofthe rotary sterilization system.

[0010] In order to prevent such loss, a number of approaches have beendiscussed and proposed for on-line control of sterilization processes.However, all of these approaches concern control of batch sterilizationprocesses performed on a batch of containers {1, . . . , i, . . . ,I}_(batch). In a batch sterilization process, all of the containersgenerally receive the same time-temperature treatment whether or not atemperature deviation occurs. Thus, when a deviation does occur, acorrection to the process can be made which simultaneously effects allof the containers so that a minimum total lethality F_(i) over [t_(b),t_(e)] will be delivered to the product cold spot of each container i,where t_(b) and t_(e) are the begin and end times of the batchsterilization process. An example of such an approach is described inconcurrently filed and co-pending U.S. Pat. application Ser. No.09/______, entitled Controller and Method for Administering andProviding On-Line Correction of a Batch Sterilization Process, filed onNov. 6, 1998, with Weng, Z. as named inventor. This patent applicationis hereby explicitly incorporated by reference.

[0011] In contrast, each container i in a rotary sterilization processwill receive a unique time-temperature treatment. Thus, the totallethality F_(i) over [t_(f,i), t_(d,i)] that is actually delivered toeach container is different. This makes it difficult to identify, whileon-line and in real time, each container that will have a predictedtotal lethality delivered to it that is below the target total lethalityF_(targ). As a result, the development of a controller that provideson-line handling of a temperature deviation in a rotary sterilizationprocess without stopping the reels of the cooking and cooling shells hasbeen inhibited.

SUMMARY OF THE INVENTION

[0012] In summary, the present invention comprises a rotarysterilization system, a controller for use in the rotary sterilizationsystem, and a method performed by the controller. The system,controller, and method are used to administer a sterilization processperformed on a line of containers and provide on-line handling of adeviation in a scheduled parameter during the process. The containerscontain a shelf stable food product that is to be sterilized in thesterilization process. In addition to the controller, the rotarysterilization system includes a rotary sterilizer.

[0013] The controller controls the rotary sterilizer in performing therotary sterilization process according to scheduled parameters. When atemperature deviation below a specific scheduled temperature occurs, thecontroller identifies those of the containers that will in response havea total lethality predicted to be delivered to them during the rotarysterilization process that is less than a predefined target lethality.This specific scheduled parameter may be a scheduled retort temperaturein a temperature zone of the rotary sterilizer through which the line ofcontainers is conveyed. It also may be a scheduled initial producttemperature for the containers or a scheduled reel speed for conveyingthe containers in line through the rotary sterilizer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a block diagram of a rotary sterilization system inaccordance with the present invention.

[0015]FIG. 2 is a block diagram of a controller of the rotarysterilization system of FIG. 1.

[0016]FIG. 3 is an overall process flow diagram for the controller ofFIG. 2 in controlling a rotary sterilization process performed by therotary sterilization system of FIG. 1.

[0017]FIG. 4 is a timing diagram for handling a temperature deviationaccording to the overall process flow diagram of FIG. 3.

[0018]FIG. 5 is a lethality distribution diagram showing thedistribution of lethalities for containers affected by the temperaturedeviation shown in FIG. 4.

[0019] FIGS. 6 to 9 are detailed process flow diagrams for various stepsof the overall process flow diagram of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring to FIG. 1, there is shown a rotary sterilization system100 for performing a rotary sterilization process on a continuous lineof containers {1, . . . , i, . . . , I}_(line). Each container icontains a food product that is to be sterilized during the process. Thesystem 100 comprises a rotary sterilizer 102, a programmed controller104, and a host computer 105.

[0021] 1. Exemplary Embodiment

[0022] In an exemplary embodiment, the rotary sterilizer 102 includes acooking shell 106-1 and a cooling shell 106-2 through which thecontainers {1, . . . , i, . . . ,I}_(line) are conveyed in line. Thecontainers are cooked in the cooking shell 106-1 and cooled in thecooling shell 106-2. Each of these shells has spiral tracks 108 and areel 109 to convey the containers through the shell. The reel 109imparts movement while the spiral tracks 108 provide the direction forthe containers to be conveyed through the shell 106-1 or 2.

[0023] Furthermore, a feed device 110 of the rotary sterilizer 102 feedsthe containers {1, . . . , i, . . . , I}_(line) in line to the cookingshell 106-1. The feed device is designed to prevent the escape of steamwhile loading the containers onto the reel of the cooking shell 106-1.The containers are transferred from the reel 109 of the cooking shell106-1 to the reel 109 of the cooling shell 106-2 by a transfer device112. Like the feed device, the transfer device is designed to preventthe escape of steam from the cooking shell while the containers aretransferred between the reels of the cooking and cooling shells. Thecontainers are finally off-loaded from the cooling shell's reel by adischarge device 114.

[0024] In this exemplary embodiment, the cooking shell 106-1 hasmultiple temperature zones 115-1, 2, and 3. The containers {1, . . . ,i, . . . I}_(line) are pre-cooked in the temperature zones 115-1 and 2at corresponding scheduled retort temperatures T_(sRT1) ⁰ and T_(sRT2)⁰. The zone 115-3 is used to cook the containers at a correspondingscheduled retort temperature T_(sRT3) ⁰. Similarly, the cooling shell106-3 has temperature zones 115-4 and 5 in which the containers arecooled at corresponding scheduled retort temperatures T_(sRT4) ⁰ andT_(sRT5) ⁰. However, as those skilled in the art will recognize and aswill be explained later in section 2, other embodiments do exist wherefewer or more cooking and/or cooling shells with fewer and/or moretemperature zones are used.

[0025] At each sample real time t_(r) (e.g., every 0.1 to 1 seconds) ofthe rotary sterilization process, the sensors 116-1, . . . , 4 of thehydrostatic sterilizer 102 respectively sense the actual retorttemperatures T_(aRT1)(t_(r)), . . . , T_(aRT5)(t_(r)) in thecorresponding temperature zones 115-1, . . . , 5 of the cooking andcooling shells 106-1 and 2. Similarly, the rotary sterilizer's sensor107 senses the actual reel speed v_(a)(t_(r)) of the reels of thecooking and cooling shells at each each sample real time t_(r). Finally,the feed device 110 periodically (e.g., every 20 to 30 minutes) removesa container being fed into the rotary sterilizer and a sensor 117 of therotary sterilizer senses its actual initial product temperatureT_(aIP)(t_(r)) at that time t_(r).

[0026] The controller 104 administers the rotary sterilization processby controlling the rotary sterilizer 102 and providing on-line handlingof any temperature deviations during the process. This is done inresponse to the actual initial product and retort temperaturesT_(aIP)(t_(r)) and T_(aRT1)(t_(r)), . . . , T_(aRT5)(t_(r)) sensed bythe sensors 117 and 116-1, . . . , 5 at each sample real time t_(r), theactual reel speed v_(a)(t_(r)) sensed by the sensor 107, and the actualinitial product temperature T_(aIP)(t_(r)) sensed by the sensor 117.

[0027] The host computer 105 is used to provide input information,namely input parameters and software, used by the controller 104 inadministering the rotary sterilization process. The host computer isalso used to receive, process, and display output information about theprocess which is generated by the controller.

[0028] 1.a. Hardware and Software Configuration of Controller 104

[0029] Turning to FIG. 2, the controller 104 comprises a main controlcomputer 118 that includes a microprocessor (i.e., CPU) 119, a primarymemory 120, and a secondary memory 121. The microprocessor executes anoperating system 122, a process control program 123, a processscheduling program 124, and a temperature deviation program 125 of thecontroller. The operating system and programs are loaded from thesecondary memory into the primary memory during execution.

[0030] The operating system 122 and the programs 123 to 125 are executedby the microprocessor 119 in response to commands issued by theoperator. These commands may be issued with a user interface 126 of themain control computer 118 and/or the host computer 105 via a hostcomputer interface 127 of the controller 104. The operating systemcontrols and coordinates the execution of the other programs. Data 128generated by the operating system and programs during execution and data128 inputted by the operator is stored in the primary memory. This dataincludes input information provided by the operator with the userinterface and/or the host computer via the host computer interface. Italso includes output information provided to the user interface or thehost computer via the host computer interface that is to be displayed tothe operator.

[0031] The controller 104 also comprises control circuitry 129. Thecontrol circuitry includes circuits, microprocessors, memories, andsoftware to administer the rotary sterilization process by generatingcontrol signals that control the sequential operation of the rotarysterilizer 102. As alluded to earlier, the software may be downloadedfrom the host computer 105 and provided to the control circuitry by theprocess control program 123. The control signals are generated inresponse to commands generated by this program and issued to the controlcircuitry from the microprocessor 119 via a control circuitry interface130 of the main control computer 118.

[0032] Furthermore, at each sample real time t_(r) of the rotarysterilization process, the control circuitry 129 receives sensor signalsfrom the sensors 107, 117, and 116-1, . . . , 5 that represent theactual reel speed v_(a)(t_(r)) and the actual initial product and retorttemperatures T_(aIP)(t_(r)) and T_(aRT1)(t_(r)), . . . ,T_(aRT5)(t_(r)). The control circuitry generates the control signals forcontrolling the rotary sterilizer 102 in response to these sensedparameters. These sensed parameters are also provided to themicroprocessor 119 via the control circuitry interface 130 and recordedby the process control program 123 as data 128 in the primary memory120. In this way, the process control program compiles and records inthe primary memory 120 an actual reel time-speed profile v_(a)(t), anactual initial product time-temperature profile T_(aIP)(t), and actualretort time-temperature profiles T_(aRT1)(t), . . . , T_(aRT5)(t) forthe corresponding temperature zones 115-1, . . . , 5. These profiles areused in the manner described later for providing on-line handling oftemperature deviations during the rotary sterilization process.

[0033] The sensors 116-1, . . . , 5 are preferably located in theslowest heating regions of the temperature zones 115-1, . . . , 5 toprovide conservative estimates of the actual retort temperaturesT_(aRT1)(t_(r)), . . . , T_(aRT5)(t_(r)). However, if this is notpossible, the process control program 123 may adjust the temperaturesprovided by the sensors to estimate the actual retort temperatures atthe slowest heating regions. This adjustment would be done according totemperature distribution data 128 in the primary memory 120 generatedfrom heating and cooling temperature distribution tests conducted on thetemperature zones.

[0034] As mentioned earlier, the operating system 122 and the otherprograms 123 to 125 are normally stored in the secondary memory 121 andthen loaded into the primary memory 120 during execution. The secondarymemory comprises one (or multiple) computer readable memory(ies) 132that is(are) readable by the main control computer 118 of the controller104. The computer readable memory(ies) is(are) therefore used to directthe controller in controlling the rotary sterilization process. Thecomputer readable memory(ies) may comprise a PROM (programmable readonly memory) that stores the operating system and/or the other programs.Alternatively or additionally, the computer readable memory(ies) maycomprise a magnetic or CD ROM storage disc that stores the operatingsystem and/or the other programs. The computer readable memory(ies) inthis case is(are) readable by the main control computer with a magneticor CD ROM storage disk drive of the secondary memory. Moreover, theoperating system and/or the other programs could also be downloaded tothe computer readable memory(ies) or the primary memory from the hostcomputer 105 via the host computer interface 127.

[0035] The controller 104 controls the rotary sterilization processaccording to the flow and timing diagrams of FIGS. 3 to 9. In doing so,a finite difference simulation model is used by the process schedulingprogram 124 to simulate a scheduled product cold spot time-temperatureprofile T_(CS)(t)_(i) ⁰ that applies to all of the containers {1, . . .i, . . . , I}_(line). Similarly, the temperature deviation program 125uses the model to simulate corresponding product cold spottime-temperature profiles { . . . , T_(CS)(t)_(i) ^(j), . . . } forcorresponding selected containers { . . . , i, . . . }_(sel) at eachsample real time t_(r) during a temperature deviation. This model may bethe earlier mentioned NumeriCAL model and used for both conductionheated food products and convection heated food products. Or, it may beone of the models described in the Teixeira et al., 1969 and Manson etal., 1970 references and used for conduction heated food products. Aswill be evident from the foregoing discussion, the novelty of theinvention described herein is not in which model is used, but in themanner in which it is used according to the flow and timing diagrams inFIGS. 3 to 9.

1.b. Overall Process Flow

[0036] In the first step 134 for controlling the rotary sterilizationprocess according to the overall process flow of FIG. 3, the inputparameters for the rotary sterilization process are defined and providedto the controller 104. The input parameters include a predefinedsampling time period Δt_(r) for each real time increment [t_(r)-Δt,t_(r)] from the previous sample real time t_(r)-Δt_(r) to the currentsample real time t_(r) during the process. The input parameters alsoinclude a initially scheduled product temperature T_(sIP) for the foodproduct in the containers being processed. The input parameters furtherinclude the traditional heating and cooling factors j_(h), f_(h),x_(bh), f₂, j_(c), and f_(c) to be used in the simulation model. Theheating factors j_(h), f_(h), x_(bh), and f₂ are respectively theheating time lag factor, the heating curve slope factor, the brokenheating time factor, and the broken heating curve slope factor that arepre-defined for the food product. Similarly, the cooling factors j_(c)and f_(c) are respectively the cooling time lag factor and the coolingcurve slope factor that are also pre-defined for the food product. Theinput parameters additionally include the earlier discussed thermalcharacteristic z for destroying a particular microorganism in the foodproduct and the associated reference temperature T_(REF). Also includedin the input parameters is the earlier discussed target total lethalityF_(targ) and earlier discussed scheduled retort temperatures T_(sRT1) ⁰,. . . , T_(sRT5) ⁰. Finally, the input parameters include the minimumand maximum reel speeds v_(min) and v_(max) and reel step information Sfor the reels 109 and spiral tracks 108 of the cooking and coolingshells 106-1 and 2 and length and location information L₁, . . . , L₅for the corresponding temperature zones 115-1, . . . , 5 in the shells.

[0037] In order to perform step 134, the operator issues commands withthe user interface 126 and/or the host computer 105 to invoke theprocess control program 123. Then, the operator enters the inputparameters T_(IP), j_(h), f_(h), x_(bh), f₂, j_(c), f_(c), F_(targ),T_(sRT1) ⁰, . . . , T_(sRT5) ⁰, v_(min), v_(max), S, and L₁, . . . , L₅with the user interface 126 and/or the host computer 105. The processcontrol program 123 loads the entered input parameters into the primarymemory 120 for use by the programs 123 to 125. The execution of theseprograms is controlled and coordinated by the process control program inthe manner discussed next.

[0038] The process control program 123 first invokes the processscheduling program 124. In step 135, the process scheduling programsimulates the entire rotary sterilization process to be administered toa container i to define an initially scheduled reel speed v_(s) ⁰ forthe reels of the cooking and cooling shells 106-1 and 2. This alsoresults in an initially scheduled time-temperature treatmentT_(sRT)(t)_(i) ⁰ that is to be given to each container i. This treatmentincludes pre-cooking portions at the scheduled retort temperaturesT_(sRT1) ⁰ and T_(sRT2) ⁰ over corresponding initially scheduled timedurations Δt₁ ⁰ and Δt₂ ⁰. The treatment also includes a cooking portionat the scheduled retort temperature T_(sRT3) ⁰ over a correspondinginitially scheduled time duration Δt₃ ⁰. Finally, the treatment includescooling portions at the scheduled retort temperatures T_(sRT4) ⁰ andT_(sRT5) ⁰ over corresponding initially scheduled time durations Δt₄ ⁰and Δt₅ ⁰. The precise manner in which step 135 is performed isdiscussed in greater detail in section 1.c., but will be brieflydiscussed next.

[0039] The initially scheduled reel speed v_(s) ⁰ and the initiallyscheduled total time-temperature treatment T_(sRT)(t)_(i) ⁰ are definedby using the simulation model mentioned earlier. Specifically, theprocess scheduling program 124 uses the simulation model to iterativelyand incrementally simulate an initially predicted product cold spottime-temperature profile T_(CS)(t)_(i) ⁰ that is predicted to occur atthe product cold spot of each container i during the rotarysterilization process. This simulation is based on the input parametersT_(sIP), j_(h), f_(h), x_(bh), f₂, j_(c), f_(c), and T_(sRT1) ⁰, . . . ,T_(sRT5) ⁰.

[0040] The process scheduling program 124 also iteratively andincrementally computes an initially predicted lethality F_(i) ⁰ that ispredicted to be delivered to the product cold spot of each container iduring the rotary sterilization process. In doing so, the programiteratively and incrementally computes a predicted total lethality F_(i)⁰ that satisfies the target total lethality F_(targ) and is predicted tobe delivered to the product cold spot over a simulated total timeinterval [0, Δt₁ ⁰+ . . . +Δt₅ ⁰]. This computation is made based on theproduct cold spot time-temperature profile T_(CS)(t)_(i) ⁰ over thistotal time duration and the input parameters z and T_(REF). Furthermore,the lethality equation described earlier is used to make thiscomputation, where t_(m)=0, t_(k)=Δt₁ ⁰+ . . . +Δt₅ ⁰,T_(CS)(t)=T_(CS)(t)_(i) ⁰, and F_(i)=F_(i) ⁰.

[0041] The initially predicted total lethality F_(i) ⁰ over [0, Δt₁ ⁰+ .. . +Δt₅ ⁰] is iteratively and incrementally computed until theinitially scheduled reel speed v_(s) ⁰ is determined for which thislethality satisfies the target total lethality F_(targ). Moreover, theinitially scheduled time durations Δt₁ ⁰, . . . , Δt₅ ⁰ are determinedfrom the reel speed v_(s) ⁰, the reel step information S, and thetemperature zone length and location information L₁, . . . , L₅. Thus,definition of the reel speed v_(s) ⁰ also includes definition of thepre-cooking, cooking, and cooling portions of the initially scheduledtotal time-temperature treatment T_(sRT)(t)⁰ on which the portions ofthe profile T_(CS)(t)⁰ over the time durations Δt₁ ⁰, . . . , Δt₅ ⁰ arebased.

[0042] The process control program 123 controls the administration ofthe rotary sterilization process in steps 136 to 149. In doing so, itfirst sets a counterj to zero in step 136. This counter is used to counteach time that the currently scheduled reel speed v_(s) ^(j) is adjustedduring the rotary sterilization process.

[0043] Then, at the current sample real time t_(r), the process controlprogram 123 causes the control circuitry 129 in step 137 to administerthe rotary sterilization process at the currently scheduled reel speedv_(s) ^(j) and at the scheduled retort temperatures T_(sRT1) ⁰, . . . ,T_(sRT5) ⁰ in the corresponding temperature zones 115-1, . . . , 5. Indoing so, the control circuitry appropriately controls the rotarysterilizer 102 and monitors the actual retort temperaturesT_(aRT1)(t_(r)), . . . , T_(aRT5)(t_(r)) in the correspondingtemperature zones 115-1, . . . , 5 at the time t_(r) to verify that theyare at least equal to the corresponding scheduled retort temperaturesT_(sRT1) ⁰, . . . , T_(sRT5) ⁰. In this embodiment of the controller104, the scheduled retort temperatures will remain the same throughoutthe rotary sterilization process regardless if temperature deviationsoccur in the temperature zones. Thus, if such a temperature deviationdoes occur in a particular temperature zone 115-n, then the controlcircuitry administers corrections at the time t_(r) so that the actualretort temperature T_(aRTn)(t_(r)) in the temperature zone 115-n willeventually be brought up to at least the corresponding temperatureT_(sRTn) ⁰.

[0044] Then the process control program 123 waits for the next samplereal time t_(r)=t_(r)+Δt_(r) in step 138. In step 139, this programrecords the actual retort temperatures T_(aRT1)(t_(r)), . . . ,T_(aRT5)(t_(r)) in the temperature zones 115-1, . . . , 5 at each samplereal time t_(r). By doing so, the program 123 compiles the correspondingactual retort time-temperature treatments T_(aRT1)(t), . . . ,T_(aRT5)(t). Similarly, the program records the actual initial producttemperature T_(aIP)(t_(r)) periodically sensed by the sensor 117 tocompile the actual initial product time-temperature profile T_(aIP)(t).Furthermore, the program also records the currently scheduled reel speedv_(s) ^(j) at each time t_(r). This is done to compile a time-reel speedprofile v(t) for the rotary sterilization process to provide a record ofthe changes in the reel speed v_(s) ^(j).

[0045] Then, in step 140, the process control program 123 determineswhether any temperature deviations are occurring at the time t_(r) inthe temperature zones 115-1, . . . , 5. In doing so, the program 123monitors each temperature T_(aRTn)(t_(r)) to determine if it is lessthan the corresponding scheduled cooking or cooling retort temperatureT_(sRTn) ⁰.

[0046] If no deviation is occurring, then the process control program123 proceeds to step 141. Any of the under processed containers { . . ., i, . . . }_(underpr) that were identified in step 148 for segregationand are being discharged by the discharge device 114 at the currentsample real time t_(r) are then segregated in step 141 by the dischargedevice. The process control program causes the control circuitry 129 tocontrol the discharge device 114 in performing this segregation in themanner discussed later. In step 149, the process control program setsthe currently scheduled reel speed v_(s) ^(j) to the initially scheduledreel speed v_(s) ⁰ if all of the containers { . . . , i, . . . }_(aff)affected by a temperature deviation have been discharged. Both steps 141and 149 are discussed later in more detail. The process control programthen administers the rotary sterilization process in step 137 and waitsfor the next sample real time t_(r)=t_(r)+Δt_(r) in step 138 to repeatthe steps 139 to 149.

[0047] However, if the process control program 123 does determine instep 140 that a temperature deviation is occurring in a temperature zone115-n at the current sample real time t_(r), then the process controlprogram invokes the temperature deviation program 125. In the exampleshown in FIG. 4, the temperature deviation occurs in the temperaturezone 115-3. In step 142, the program 125 identifies the container i thatcurrently at the time t_(r) has the minimum total lethality F_(i) ^(j)predicted to be delivered to its product cold spot over its currentlyscheduled total time interval [t_(f,i), t_(d,i) ^(j)]. This minimumlethality container i is identified from among the containers { . . . ,i, . . . }_(aff) that are currently affected by the temperaturedeviation. These affected containers are those of the containers {1, . .. , i, . . . , I}_(line) that are at the time t_(r) currently in thetemperature zone 115-n in which the temperature deviation is occurring.This is determined using the reel step information S, the reeltime-speed profile v(t) compiled in step 139, and the length andlocation information L₁, . . . , L₅ for the temperature zones 115-1, . .. , 5.

[0048] In one approach for identifying the minimum lethality container ifrom among the affected containers { . . . , i, . . . }_(aff), thetemperature deviation program 125 may use an optimization searchtechnique, such as the Brendt method disclosed in Press, W. H.,Teukolsky, S. A., Vettering, W. T., and Flannery, B. P., NumericalRecipes in Fortran: The Art of Scientific Computing, CambridgeUniversity Press, 1992. In this case, the program iteratively computespredicted total lethalities { . . . , F_(i) ^(j) over [t_(f,i), t_(d,i)^(j)], . . . }_(sel) for containers { . . . , i, . . . }_(sel) selectedto be evaluated. Based on these lethalities, the program iterativelybisects the list of affected containers to select the selectedcontainers from among the affected containers until the minimumlethality container i is identified.

[0049] In a variation of the approach just described, the temperaturedeviation program 125 may initially use predefined intervals toinitially select containers { . . . , i, . . . }_(int) at the intervalsfor evaluation. Then, around those of the initially selected containersthat have the lowest predicted total lethalities {. . . , F_(i) ^(j)over [t_(f,i), t_(d,i) ^(j)], . . . }_(int), the optimization searchtechnique just described is used.

[0050] In still another approach for identifying the minimum lethalitycontainer i, the temperature deviation program 125 may select all of theaffected containers { . . . , i, . . . }_(aff) as the selectedcontainers { . . . , i, . . . }_(sel) for evaluation. In doing so, theprogram computes at each sample real time t_(r) the predicted totallethality F_(i) ^(j) over [t_(f,i), t_(d,i) ^(j)] for each container i.From the computed lethalities {. . . , F_(i) ^(j) over [t_(f,i), t_(d,i)^(j)], . . . }_(sel) for the selected containers, the minimum lethalitycontainer i is identified.

[0051] In each of the approaches just described, the predicted totallethality F_(i) ^(j) over [t_(f,i), t_(d,i) ^(j)] for each selectedcontainer i is computed in the same way. Specifically, the temperaturedeviation program 125 first computes an actual current lethality F_(i)^(j) delivered to the container's product cold spot over the actual timeinterval [t_(f,i), t_(r)] that the container has been in the rotarysterilizer 102. This is done by simulating the portion of the rotarysterilization process that was actually administered over this timeinterval. In doing so, the simulation model mentioned earlier is used toiteratively and incrementally simulate the actual portion of the productcold spot time-temperature profile T_(CS)(t)_(i) ^(j) over this timeinterval for the container i. This is done based on the input parametersj_(h), f_(h), x_(bh), f₂, j_(c), and f_(c), the actual initial producttemperature T_(aIP)(t_(f,i)) for the container i, and the portions ofthe actual retort time-temperature profiles T_(aRT1)(t), . . . ,T_(aRTn)(t) respectively over the actual time intervals [t_(f,i),t_(1,i) ^(j)], . . . , (t_(n-1,i) ^(j), t_(r)] that the container was inthe temperature zones 115-1, . . . , n. Here, n identifies thetemperature zone 115-n in which the temperature deviation is occurring.As mentioned earlier, in the example of FIG. 4, this is the temperaturezone 115-3.

[0052] The actual initial product temperature T_(aIP)(t_(f,i)) for thecontainer i is obtained from the actual initial product time-temperatureprofile T_(aIP)(t) compiled in step 139. The actual time intervals[t_(f,i), t_(1,i) ^(j)], . . . , (t_(n-1,) ^(j), t_(r)] for the selectedcontainer i are determined by the temperature deviation program 125 fromthe reel time-speed profile v(t), the reel step information S, and thetemperature zone length and location information L_(l), . . . , L_(n).

[0053] In the example of FIG. 4, the temperature deviation occurs in thetemperature zone 115-3. Thus, the portion of the product cold spottemperature profile T_(CS)(t)_(i) ^(j) that actually occurred over theactual time interval [t_(f,i), _(r)] is based in this case on theportions of the actual retort time-temperature profiles T_(aRT1)(t),T_(aRT2)(t), and T_(aRT3)(t) respectively over the actual time intervals[t_(f,i), t_(1,i) ^(j)], (t_(1,i) ^(j), t_(2,i) ^(j),], and (t_(2,i)^(j), t_(r)]. The time intervals [t_(f,i), t_(1,i) ^(j)] and (t_(1,i)^(j), t_(2,i) ^(j),] have the initially scheduled time durations Δt₁ ⁰and Δt₂ ⁰ since the temperature deviation began at the deviation begintime t_(e) while the container i was in the temperature zone 115-3. If,however, this container was in another temperature zone 115-1 or 2 whenthe deviation began, then the time intervals [t_(f,i), t_(1,i) ^(j)]and/or (t_(1,i) ^(j), t_(2,i) ^(j),] would have different time durationsΔt₁ ^(j) and/or Δt₂ ^(j) because the reel speed v_(s) ^(j) would havebeen changed while the container was in that temperature zone.

[0054] From the actual portion of the product cold spot time-temperatureprofile T_(CS)(t)_(i) ^(j) over [t_(f,i), t_(r)] and the inputparameters z and T_(REF), the temperature deviation program 125iteratively and incrementally computes the actual current lethalityF_(i) ^(j) that has been delivered to the product cold spot of theselected container i over the actual time interval [t_(f,i), t_(r)].This is done using the lethality equation described earlier, wheret_(m)=t_(f,i), t_(k)=t_(r), T_(CS)(t)=T_(CS)(t)_(i) ^(j), andF_(i)=F_(i) ^(j). The precise manner in which the actual currentlethality is computed in step 142 is discussed in greater detail insection 1.d.

[0055] Then, the temperature deviation program 125 simulates theremaining portion of the rotary sterilization process that is predictedto be administered to the selected container i over the scheduledremaining time interval (t_(r), t_(d,i) ^(j)] assuming that thetemperature deviation ends after the time t_(r). In performing thissimulation, the simulation model mentioned earlier is used toiteratively simulate the predicted remaining portion of the product coldspot time-temperature profile T_(CS)(t)_(i) ^(j) based on the inputparameters j_(h), f_(h), X_(bh), f₂, j_(c), and f_(c), the actualproduct cold spot temperature T_(CS)(t_(r))_(i) ^(j) at the time t_(r),and the scheduled retort temperatures T_(sRTn) ⁰, . . . , T_(sRT5) ⁰over the currently scheduled remaining time intervals (t_(r), t_(n,i)^(j)], . . . , t_(4,i) ^(j),t_(d,i) ^(j)].

[0056] The actual product cold spot temperature T_(CS)(t_(r))_(i) ^(j)for the selected container i is obtained from the actual portion of theproduct cold spot time-temperature profile T_(CS)(t)_(i) ^(j) over[t_(f,i), t_(r)] that was just described. Moreover, the currentlyscheduled time intervals (t_(r), t_(n,i) ^(j)], . . . , (t_(4,i)^(j),t_(d,i) ^(j)] for the container i are determined by the temperaturedeviation program 125 from the reel time-speed profile v(t), the reelstep information S, and the temperature zone length and locationinformation L₁, . . . , L₅.

[0057] In the example of FIG. 4, the temperature deviation occurs in thetemperature zone 115-3. Thus, the predicted remaining portion of theproduct cold spot temperature profile T_(CS)(t)_(i) ^(j) is based on thescheduled retort temperatures T_(sRT3) ⁰, T_(sRT4) ⁰, and T_(sRT5) ⁰respectively over the currently scheduled remaining time intervals(t_(r), t_(3,i) ^(j)], (t_(3,i) ^(j),t_(4,i) ^(j)], and (t_(4,i)^(j),t_(d,i) ^(j)]. In this example, the time intervals (t_(2,i) ^(j),t_(3,i) ^(j)], (t_(3,i) ^(j),t_(4,i) ^(j)] and (t_(4,i) ^(j),t_(d,i)^(j)] respectively have re-scheduled time durations Δt₃ ^(j), Δt₄ ^(j),and Δt₅ ^(j) that are different than the initially scheduled timedurations Δt₃ ⁰, Δt₄ ⁰, and Δt₅ ⁰ since the currently scheduled reelspeed v_(s) ^(j) at the current sample real time t_(r) has beenre-scheduled from the initially scheduled reel speed v_(s) ⁰.

[0058] The temperature deviation program 125 iteratively andincrementally computes the total lethality F_(i) ^(j) predicted to bedelivered to the product cold spot of the selected container i over thescheduled total time interval [t_(f,i), t_(d,i) ^(j)]. This is donebased on the predicted remaining portion of the product cold spottime-temperature profile T_(CS)(t)_(i) ^(j) over (t_(r), t_(d,i) ^(j)],the actual current lethality F_(i) ^(j) over [t_(f,i), t_(r)] that wasjust described, and the input parameters z and T_(REF). This is alsodone using the lethality equation described earlier, where t_(m)=t_(r),t_(k)=t_(d,i) ^(j), T_(CS)(t)=T_(CS)(t)_(i) ^(j), and F_(i)=F_(i) ^(j).The predicted total lethality is the sum of the actual current lethalityand a predicted remaining lethality F_(i) ^(j) that is predicted to bedelivered to the container's product cold spot over the time interval[t_(r), t_(d,i) ^(j)]. The precise manner in which the predicted totallethality is computed in step 142 is discussed in greater detail insection 1.e.

[0059] Then, in step 143, the temperature deviation program 125determines at the current sample real time t_(r) if the container i withthe minimum predicted total lethality F_(i) ^(j) over [t_(f,i), t_(d,i)^(j)] is less than the target total lethality F_(targ). If it is not,then this means that all of the affected containers { . . . , i, . . .}_(aff) also have predicted total lethalities { . . . , F_(i) ^(j) over[t_(f,i), t_(d,i) ^(j)], . . . }_(aff) that are at least equal to thetarget total lethality. In this case, the process control program 123proceeds to step 141 and causes any of the previously identified underprocessed containers { . . . , i, . . . }_(underpr) that are beingdischarged at the time t_(r) to be segregated. Then, in the mannerdiscussed earlier, the process control program 123 administers therotary sterilization process in step 137 and waits for the next samplereal time t_(r)=t_(r)+Δt_(r) in step 138 to repeat the steps 139 to 148.

[0060] In this embodiment, if it is determined in step 143 that theminimum total lethality F_(i) ^(j) over [t_(f,i), t_(d,i) ^(j)] is lessthan the target total lethality F_(targ), then the temperature deviationprogram 125 determines in step 144 if the currently scheduled reel speedv_(s) ^(j) is set to the minimum reel speed v_(min). If it is not, thenthe program increments the counter j in step 145 and defines are-scheduled (or adjusted) reel speed v_(s) ^(j) in step 146.

[0061] In step 146, the re-scheduled reel speed v_(s) ^(j) is defined ina similar manner to the way in which the initially scheduled reel speedv_(s) ⁰ is defined in step 135. But, in this case the actual productcold spot temperature T_(CS)(t_(r))_(i) ^(j) at the time t_(r) and theactual current lethality F_(i) ^(j) over [t_(f,i), t_(r)] for theminimum lethality container i are used in simulating the remainingportion of the rotary sterilization process in order to compute apredicted total lethality F_(i) ^(j) over [t_(f,i), t_(d,i) ^(j)]. Thisis done in a similar manner to that described earlier for computing thepredicted total lethality for a container in step 142. But, similar tostep 135, this is done iteratively and incrementally until the reelspeed is determined for which the predicted total lethality satisfiesthe total target lethality F_(targ) or the reel speed equals the minimumreel speed v_(min). The precise manner in which step 146 is performed isdiscussed in greater detail in section 1.f, but will be brieflydiscussed next.

[0062] The definition of the re-scheduled reel speed therefore alsoresults in the definition of a re-scheduled remaining time-temperaturetreatment T_(sRT)(t)_(i) ^(j). The treatment includes a remainingcooking portion at the scheduled retort temperature T_(sRT3) ⁰ over acorresponding re-scheduled time duration Δt₃ ^(j). Similarly, thetreatment also includes cooling portions at the scheduled retorttemperatures T_(sRT4) ⁰ and T_(sRT5) ⁰ over corresponding re-scheduledtime durations Δt₄ ^(j) and Δt₅ ^(j).

[0063] Ideally, it is desired that the minimum predicted total lethalityF_(i) ^(j) over [t_(f,i), t_(d,i) ^(j)] for the minimum lethalitycontainer i will satisfy the target total lethality F_(targ). But, asjust mentioned, the re-scheduled reel speed v_(s) ^(j) may be limited tothe minimum reel speed v_(min). In this case, the minimum predictedtotal lethality will not satisfy the target total lethality F_(targ). Ifthe temperature deviation program 125 determines this to be the case instep 147, then this means that under processed containers { . . . , i, .. . }_(underpr) from among the affected containers { . . . , i, . . .}_(aff) will have predicted total lethalities { . . . , F_(i) ^(j) over[t_(f,i), t_(d,i) ^(j)], . . . }_(underpr) that are less than the targettotal lethality. The minimum lethality container i is of course one ofthe under processed containers. The under processed containers are to besegregated and are identified at the current real sample time t_(r) instep 148 by the program.

[0064]FIG. 5 shows the distribution of the affected containers { . . . ,i, . . . }_(aff) and the under processed containers { . . . , i, . . .}_(underpr) to be segregated at the time t_(r). In identifying the underprocessed containers in step 148, the program 125 uses a similarapproach as that used in step 142 to identify the minimum lethalitycontainer i. But, in this case, the additional criteria of the targettotal lethality F_(targ) is used to expand the search.

[0065] Once the under processed containers { . . . , i, . . .}_(underpr) have been identified at the current real sample time t_(r),the process control program 123 then proceeds to step 141. As discussedearlier, this program causes the control circuitry 129 to control thedischarge device 114 in segregating any of the under processedcontainers that are being discharged at the current sample real timet_(r). In order to segregate the under processed containers, the processcontrol program tracks these containers to determine when they will bedischarged. This is done using the reel time-speed profile v(t), thereel step information S, and the temperature zone length and locationinformation L₁, . . . , L₅.

[0066] The steps 137 to 149 are repeated until the temperature deviationis cleared. In this way, at each sample real time t_(r) during thedeviation, the list of under processed containers { . . . , i, . . .}_(underpr) at the time t_(r) is combined with the list from theprevious sample real time t_(r). As a result, the list of underprocessed containers is dynamically updated and maintained. Since theseunder processed containers are segregated when discharged in step 141,this will ensure that only those of the containers {1, . . . , i, . . .I}_(line) that are adequately processed are released for distribution.

[0067] The list of affected containers { . . . , i, . . . }_(aff) isalso dynamically updated and maintained in the same manner as the listof under processed containers { . . . , i, . . . }_(underpr). When thetemperature deviation is cleared, this list will remain the same and theprocess control program 123 tracks the containers in this list untilthey have all been discharged. This tracking is done in the same mannerin which the under processed containers are tracked. The process controlprogram 123 will then set the currently scheduled reel speed v_(s) ^(j)back to the initially scheduled reel speed v_(s) ⁰ in step 149.

[0068] Furthermore, the controller 104 has the unique feature of beingable to handle multiple temperature deviations. For example, if anothertemperature deviation does occur, then the steps 137 to 149 are repeatedduring this deviation. Therefore, even if a selected container i isexposed to multiple temperature deviations, the predicted totallethality F_(i) ^(j) over [t_(f,i), t_(d,i) ^(j)] that will be deliveredto it can be accurately determined based on those of the actual retorttemperature profiles T_(aRT1)(t), . . . , T_(aRT5)(t) that it has beentreated with over the rotary sterilization process. Moreover, thisresults in the list of under processed containers { . . . , i, . . .}_(underpr) being further updated and expanded.

[0069] 1.c. Detailed Process Flow for Step 135 of FIG. 3

[0070]FIG. 6 shows the detailed process flow that the process schedulingprogram 124 uses in step 135 of FIG. 3 to define the initially scheduledreel speed v_(s) ⁰. In doing so, this program iteratively performs asimulation of the rotary sterilization process that is predicted to beadministered to each container i in sub-steps 150 to 160 of step 135.

[0071] In step 150, the process scheduling program 124 first defines theinitially scheduled reel speed v_(s) ⁰ as the maximum reel speedv_(max). Then, in step 151, the program defines the time durations Δt₁⁰, . . . , Δt₅ ⁰ for how long each container i is scheduled to be in therespective temperature zones 115-1, . . . , 5. This is done based on theinitially scheduled reel speed, the reel step information S for thereels 109 and spiral tracks 108 of the cooking and cooling shells 106-1and 2, and the length and location information L₁, . . . , L₅ for thetemperature zones.

[0072] In step 152, the current sample simulation time t_(s) isinitially set to zero by the process scheduling program 124. This is thebegin time of the simulated rotary sterilization process for thecontainer i. The program also initially sets the predicted product coldspot temperature T_(CS)(t_(s))_(i) ⁰ of the container's product coldspot at this time to the scheduled initial product temperature T_(sIP).Similarly, the lethality F_(i) ⁰ predicted to be delivered to theproduct cold spot over the current simulation time interval [0, t_(s)]is initially set by the program to zero.

[0073] Steps 153 to 157 are then performed by the process schedulingprogram 124 in each iteration of the simulation. In step 153 of eachiteration, the program increments the current sample simulation timet_(s) by the amount of the sampling period Δt_(r). This results in a newcurrent sample simulation time t_(s).

[0074] Then, in step 154 of each iteration, the process schedulingprogram 124 simulates the portion of the product cold spottime-temperature profile T_(CS)(t)_(i) ⁰ predicted to occur at theproduct cold spot of the container i over the current simulation timeincrement [t_(s)-Δt_(r), t_(s)]. This is done using the simulation modeldiscussed earlier and is based on the predicted product cold spottemperature T_(CS)(t_(s)-Δt_(r))_(i) ⁰ for the product cold spot at theprevious sample simulation time t_(s)-Δt_(r) and the heating and coolingfactors j_(h), f_(h), x_(bh), f₂, j_(c), and f_(c). In the firstiteration, this product cold spot temperature will be the scheduledinitial product temperature T_(sIP) from step 152. However, in eachsubsequent iteration, the product cold spot temperature is obtained fromthe portion of the product cold spot temperature profile predicted overthe previous simulation time increment [t_(s)-2Δt_(r), t_(s)-Δt_(r)]that was simulated in step 154 of the previous iteration. Moreover, thesimulation is also based on the respective scheduled retort temperaturesT_(sRT1) ⁰, . . . , T_(sRT5) ⁰ when the current sample simulation timet_(s) is within the corresponding simulation time intervals [0, Δt₁ ⁰],. . . , [Δt₁ ⁰+. . . +Δt₄ ⁰, Δt₅ ⁰]. These time intervals indicate howlong the container i is scheduled to be in the respective temperaturezones 115-1, . . . , 5.

[0075] The lethality F_(i) ⁰ that is predicted to be delivered to theproduct cold spot of the container i over the current simulation timeincrement [t_(s)-Δt_(r), t_(s)] is then computed by the processscheduling program 124 in step 155 of each iteration. This is done basedon the portion of the product cold spot time-temperature profileT_(CS)(t)_(i) ⁰ predicted over this time increment and the inputparameters z and T_(REF). This is also done in accordance with thelethality equation described earlier, where t_(m)=t_(s)-Δt_(r),t_(k)=t_(s), T_(CS)(t)=T_(CS)(t)_(i) ⁰, and F_(i)=F_(i) ⁰.

[0076] In step 156 of each iteration, the process scheduling program 124computes the lethality F_(i) ⁰ predicted to be delivered to the productcold spot of the container i over the current simulation time interval[0, t_(s)]. This is done by adding the predicted lethality F_(i) ⁰ overthe current simulation time increment [t_(s)-Δt_(r), t_(s)] in step 154to the lethality F_(i) ⁰ predicted to be delivered to the product coldspot over the previous simulation time interval [0, t_(s)-Δt_(r)]. Inthe first iteration, the predicted lethality over the previoussimulation time interval is zero from step 152. In each subsequentiteration, this lethality is computed in step 156 of the previousiteration.

[0077] Then, in step 157 of each iteration, the process schedulingprogram 124 determines whether the current simulation time t_(s) hasreached the end time [Δt₁ ⁰+ . . . +Δt₅ ⁰] of the simulated rotarysterilization process for the container i. If it is not, then theprogram returns to step 153 for the next iteration. In this way, steps153 to 157 are repeated in each subsequent iteration until it isdetermined that the end time for the simulated rotary sterilizationprocess has been reached. When this finally occurs, the program sets instep 158 the lethality F_(i) ^(j) over the current simulation timeinterval [0, t_(s)] to the total lethality F_(i) ^(j) predicted to bedelivered to the container's product cold spot over the total simulationtime interval [0, Δt₁ ⁰+ . . . +Δt₅ ⁰].

[0078] When this finally occurs, the process scheduling program 124determines in step 158 whether the predicted total lethality F_(i) ⁰over [0, Δt₁ ⁰+ . . . +Δt₅ ⁰] is at least equal to the target totallethality F_(targ). If it is not, then the program decrements in step160 the initially scheduled reel speed v_(s) ⁰ by a predefined reelspeed offset Δv. This results in the re-definition of this reel speed.Steps 151 to 160 are then repeated until step 159 is satisfied. The reelspeed for which step 159 is satisfied is then used in steps 136 to 148of FIG. 3 in the manner discussed earlier.

[0079] 1.d. Detailed Process Flow for Computing Lethality F_(i) ^(j)over [t_(f,i), t_(r)) in Steps 142 and 148 of FIG. 3

[0080]FIG. 7 shows the detailed process flow that the temperaturedeviation program 125 uses in steps 142 and 148 of FIG. 3 to compute theactual current lethality F_(i) ^(j) delivered to the product cold spotof the container i over the actual time interval [t_(f,i), t_(r)] thatthe container has been in the rotary sterilizer 102. This is done byiteratively performing sub-steps 161 to 168 of steps 142 and 148 tosimulate the actual portion of the rotary sterilization process that hasbeen administered to the container's product cold spot over this timeinterval. Here, steps 161 to 168 are respectively similar to steps 151to 158 of FIG. 6 and discussed in section 1.c., except for thedifferences discussed next.

[0081] In step 161, the temperature deviation program 125 defines theactual time intervals [t_(f,i), t_(1,i) ^(j)], . . . , (t_(n−1,i) ^(j),t_(r)] that the container i has actually been in the respectivetemperature zones 115-1, . . . , n up to the current sample real timet_(r). In this step, the definition of these time intervals is based onthe accumulated reel time-speed profile v(t).

[0082] In step 162, the temperature deviation program 125 initially setsthe product cold spot temperature T_(CS)(t_(s))_(i) ^(j) for the productcold spot of the container i at the initial sample simulation time t_(s)to the actual initial product temperature T_(aIP)(t_(f,i)). Thistemperature is obtained from the actual initial product time-temperatureprofile T_(aIP)(t). Moreover, the program initially sets the actuallethality F_(i) ^(j) delivered to the product cold spot over the currentsimulation time interval [t_(f,i), t_(s)] to zero.

[0083] In step 164 of each iteration, the process scheduling program 124simulates the portion of the product cold spot time-temperature profileT_(CS)(t)_(i) ^(j) that actually occurred at the product cold spot ofthe container i over the current simulation time increment[t_(s)-Δt_(r), t_(s)]. This simulation is based on the respective actualretort temperatures T_(aRT1)(t_(s)), . . . , T_(aRTn)(t_(s)) when thecurrent simulation time t_(s) is within the corresponding simulationtime intervals [t_(f,i), t_(1,i) ^(j)], . . . , (t_(n−1,i) ^(j), t_(r)].These actual retort temperatures are obtained from the correspondingactual retort time-temperature profiles T_(aRT1)(t), . . . ,T_(aRTn)(t).

[0084] The actual lethality F_(i) ^(j) that was delivered to the productcold spot of the container i over the current simulation time increment[t_(s)-Δt_(r), t_(s)] is then computed by the temperature deviationprogram 125 in step 165 of each iteration. This is done based on theactual portion of the product cold spot time-temperature profileT_(CS)(t)_(i) ^(j) that was simulated over this time increment. In thiscase, T_(CS)(t)=T_(CS)(t)_(i) ^(j) and F_(i)=F_(i) ^(j) in the lethalityequation described earlier.

[0085] In step 166 of each iteration, the temperature deviation program125 computes the actual lethality F_(i) ^(j) delivered to the productcold spot of the container i over the current simulation time interval[t_(f,i), t_(s)]. This is done by adding the actual lethality F_(i) ^(j)over the current simulation time increment [t_(s)-Δt_(r), t_(s)] in step164 to the actual lethality F_(i) ^(j) over the previous simulation timeinterval [t_(f,i), t_(s)-Δt_(r)].

[0086] Then, in step 167 of each iteration, the temperature deviationprogram 125 determines whether the current simulation time t_(s) hasreached the current sample real time t_(r). If it is not, then theprogram returns to step 163 for the next iteration. In this way, steps163 to 167 are repeated in each subsequent iteration until it isdetermined that the current sample real time has been reached. When thisfinally occurs, the temperature deviation program 125 sets in step 168the lethality F_(i) ^(j) over the current simulation time interval[t_(f,i), t_(s)] to the actual current lethality F_(i) ^(j) over theactual time interval [t_(f,i), t_(r)] and the product cold spottemperature T_(CS)(t_(s))_(i) ^(j) for the container at the currentsample simulation time to the actual product cold spot temperatureT_(CS)(t_(r))_(i) ^(j) at the current sample real time.

[0087] 1.e. Detailed Process Flow for Computing Lethality F_(i) ^(j)over [t_(f,i), t_(d,i) ^(j)] in Steps 142 and 148 of FIG. 3

[0088]FIG. 8 shows the detailed process flow that the temperaturedeviation program 125 uses in steps 142 and 148 of FIG. 3 to compute thelethality F_(i) ^(j) predicted to be delivered to the product cold spotof a selected container over the total time interval [t_(f,i), t_(d,i)^(j)] that the container is in the rotary sterilizer 102. In this case,the program iteratively performs a simulation of the predicted remainingportion of the rotary sterilization process to be administered to thiscontainer using sub-steps 169 to 176 of steps 142 and 148. Like steps161 to 168, steps 169 to 176 are respectively similar to steps 151 to158 of FIG. 6 and discussed in section 1.c., except for the differencesdiscussed next.

[0089] In step 169, the temperature deviation program 125 defines theremaining time intervals (t_(r), t_(n,1) ^(j)], . . . , (t_(4,i) ^(j),t_(d,i) ^(j)] that the container i is predicted to be in the respectivetemperature zones 115-n, . . . , 5 after the current sample real timet_(r). The definition of these time intervals in step 169 is based onthe currently scheduled reel speed v_(s) ^(j).

[0090] In step 170, the temperature deviation program 125 initially setsthe initial sample simulation time t_(s) to the current sample real timet_(r). The program also initially sets the predicted product cold spottemperature T_(CS)(t_(s))_(i) ^(j) for the product cold spot of thecontainer i at this sample simulation time to the actual product coldspot temperature T_(CS)(t_(r))_(i) ^(j) obtained from step 168 of FIG.7. Moreover, the program initially sets the predicted lethality F_(i)^(j) to be delivered to the product cold spot over the currentsimulation time interval [t_(f,i), t_(s)] to the actual lethality F_(i)^(j) over the actual time interval [t_(f,i), t_(r)] also obtained fromstep 168.

[0091] In step 172 of each iteration, the temperature deviation program125 simulates the portion of the product cold spot time-temperatureprofile T_(CS)(t)_(i) ^(j) that is predicted to occur at the productcold spot of the container i over the current simulation time increment[t_(s)-Δt_(r), t_(s)]. The simulation is based on the respectivescheduled retort temperatures T_(sRTn) ⁰, . . . , T_(sRT5) ⁰ when thecurrent simulation time t_(s) is within the corresponding simulationtime intervals (t_(r), t_(n,i) ^(j)], . . . , (t_(4,i) ^(j), t_(d,i)^(j)].

[0092] The lethality F_(i) ^(j) that is predicted to be delivered overthe current simulation time increment [t_(s)-Δt_(r), t_(s)] is thencomputed by the temperature deviation program 125 in step 173 of eachiteration. This is done based on the predicted portion of the productcold spot time-temperature profile T_(CS)(t)_(i) ^(j) that was simulatedover this time increment in step 172.

[0093] In step 174 of each iteration, the temperature deviation program125 computes the lethality F_(i) ^(j) predicted to be delivered to theproduct cold spot of the container i over the current simulation timeinterval [t_(f,i), t_(s)]. This is done by adding the predictedlethality F_(i) ^(j) over the current simulation time increment[t_(s)-Δt_(r), t_(s)] from step 173 to the predicted lethality F_(i)^(j) over the previous simulation time interval [t_(f,i), t_(s)-Δt_(r)].

[0094] Then, in step 175 of each iteration, the temperature deviationprogram 125 determines whether the current sample simulation time t_(s)has reached the predicted discharge time t_(d,i) ^(j) for the containeri. If it has not, then the program returns to step 171 for the nextiteration. In this way, steps 171 to 175 are repeated in each subsequentiteration until it is determined that the predicted discharge time hasbeen reached. When this finally occurs, the program sets in step 176 thelethality F_(i) ^(j) over the current simulation time interval [t_(f,i),t_(s)] to the predicted lethality. F_(i) ^(j) over the currentlyscheduled total time interval [t_(f,i), t_(d,i)].

[0095] 1.f. Detailed Process Flow for Step 146 of FIG. 3

[0096]FIG. 9 shows the detailed process flow that the temperaturedeviation program 125 uses in step 146 of FIG. 3 to define there-scheduled reel speed v_(s) ^(j). This program uses sub-steps 178 to187 to iteratively perform a simulation of the remaining portion of therotary sterilization process predicted to be administered to the minimumlethality container i identified in step 142 of FIG. 3 and discussed insection 1.b. Steps 178 to 187 are respectively similar to steps 159 and151 to 159 of FIG. 6 and discussed in section 1.c., except for thedifferences discussed next.

[0097] In step 178, the temperature deviation program 125 firstdecrements the currently scheduled reel speed v_(s) ^(j) by thepredefined reel speed offset Δv. If the decremented reel speed isgreater than the minimum reel speed v_(min), the re-scheduled reel speedis defined as the decremented reel speed. However, if the decrementedreel speed is less than or equal to the minimum reel speed, then there-scheduled reel speed is defined as the minimum reel speed.

[0098] Since a re-scheduled reel speed v_(i) ^(j) is defined in step178, the re-scheduled remaining time intervals (t_(r), t_(n,i) ^(j)], .. . , (t_(4,i) ^(j), t_(d,i) ^(j)] that the minimum lethality containeri is predicted to be in the respective temperature zones 115-n, . . . ,5 after the current sample real time t_(r) need to be defined. This isdone in step 179.

[0099] Step 180 to 186 are the same as steps 170 to 176 of FIG. 8 anddiscussed in section 1.e. Thus, these steps are used to compute a totallethality F_(i) ^(j) predicted to be delivered to the product cold spotof the minimum lethality container i over the re-scheduled total timeinterval [t_(f,i), t_(d,i) ^(j)]. It should be noted here that this isdone using the actual current lethality F_(i) ^(j) over [t_(f,i), t_(r)]and the actual product cold spot temperature T_(CS)(t_(r))^(j) for theminimum lethality container i computed in steps 161 to 168 of FIG. 7.

[0100] Then, in step 187, the temperature deviation program 125determines if the predicted total lethality F_(i) ^(j) over [t_(f,i),t_(d,i) ^(j)] satisfies the target total lethality F_(targ). If it doesnot, then the program determines in step 188 whether the re-scheduledreel speed v_(s) ^(j) equals the minimum reel speed v_(min). If it doesnot, then steps 181 to 188 are repeated until it is determined in step187 that the target lethality has been satisfied or it is determined instep 188 that the minimum reel speed has been reached. In this way, thereel speed is re-scheduled.

[0101] 2. Alternative Embodiments

[0102] As indicated earlier, the embodiment of controller 104 associatedwith FIGS. 3 to 9 and described in section 1. is an exemplaryembodiment. Alternative embodiments that utilize the principles andconcepts developed in FIGS. 3 to 9 and section 1. do exist. Some ofthese embodiments are discussed next.

[0103] 2.a. Scheduling and Re-Scheduling Variations

[0104] The operator of the rotary sterilization process 100 may want tokeep the initially scheduled reel speed v_(s) ⁰ and retort temperaturesT_(sRT1) ⁰, . . . , T_(sRT5) ⁰ constant throughout the entire rotarysterilization process. Thus, in this embodiment, the temperaturedeviation program 125 is simply used to identify the under processedcontainers { . . . , i, . . . }_(underpr) in the manner discussedearlier in section 1.b. when a temperature deviation occurs. Morespecifically, the steps 145 to 147 would be eliminated from the flowdiagram of FIG. 3.

[0105] In another embodiment, the initially scheduled retorttemperatures T_(sRT1) ⁰, . . . , T_(sRT5) ⁰ may be re-scheduled when atemperature deviation occurs. In this case, the temperature deviationprogram 125 would define a re-scheduled retort temperature T_(sRT1)^(j), . . . , or T_(sRT5) ^(j) in a similar manner to which it defined are-scheduled reel speed v_(s) ^(j) in step 146 of FIG. 3 and steps 178to 188 of FIG. 9. In this embodiment, the initially scheduled reel speedv_(s) ⁰ may be kept constant or a re-scheduled reel speed v_(s) ^(j) maybe defined in conjunction with the re-scheduled retort temperature.

[0106] 2.b. Identifying and Segregating Over Processed Containers

[0107] Since re-scheduled reel speed v_(s) ^(j) may be defined when atemperature deviation occurs, it is possible that some of the containers{1, . . . , i, . . . , I} may be over processed due to the slowerre-scheduled reel speed. In this case, a maximum total lethality F_(max)may be pre-defined and included as one of the input parameters. Then,the over processed containers { . . . , i, . . . }_(overpr) withpredicted total lethalities { . . . , F_(i) ^(j) over [t_(f,i), t_(d,i)^(j)], . . . }_(overpr) over this maximum total lethality would beidentified in a similar manner to that way in which the under processedcontainers { . . . , i, . . . }_(underpr) are identified in step 148 ofFIG. 3 and discussed in section 1.b. These containers would besegregated in the same way that the under processed containers aresegregated in step 141 of FIG. 3. As a result, the remaining containersthat are not under or over processed would have a uniform quality foodproduct using this technique.

[0108] 2.c. More Conservative Approaches

[0109] In steps 142 and 148 of FIG. 3 discussed in section 1.b. and insteps 161 to 168 of FIG. 7 discussed in section 1.d., an aggressiveapproach was discussed for simulating the actual portion of the productcold spot time-temperature profile T_(CS)(t)_(i) ^(j) that occurs overthe actual time interval [t_(f,i), t_(r)] that a container i has been inthe rotary sterilizer 102. Specifically, this portion of the productcold spot time-temperature profile is based on the actual retorttime-temperature profiles T_(aRT1)(t), . . . , T_(aRTn)(t) over thecorresponding time intervals [t_(f,i), t_(1,i) ^(j)], . . . , (t_(n−1,i)^(j), t_(r)].

[0110] However, a more conservative embodiment could be employed whichuses only the portion of the actual retort time-temperature profileT_(aRTn)(t) over the time interval from the time when the container isfirst affected by the temperature deviation to the current sample realtime t_(r). Specifically, the portion of the product cold spottime-temperature profile T_(CS)(t)_(i) ^(j) over the time intervals[t_(f,i), t_(1,i) ^(j)], . . . , (t_(n−2,i) ^(j), t_(n−1,i) ^(j)] wouldbe based on the corresponding scheduled retort temperatures T_(sRT1) ⁰,. . . , T_(sRTn−1) ⁰ for the temperature zones 115-1, . . . , n-1 inwhich the temperature deviation is not occurring.

[0111] Thus, if the container enters the temperature zone 115-n whilethe temperature deviation is occurring, the portion of the product coldspot time-temperature profile T_(CS)(t)_(i) ^(j) over the time interval(t_(n−1,i) ^(j), t_(r)] would still be based on the portion of theactual retort time-temperature profile T_(aRTn)(t) over this timeinterval. But, if the temperature deviation begins at the deviationbegin time t_(d) while the container is in this temperature zone, thenthe portion of the product cold spot time-temperature profile over thetime interval (t_(n−1,i) ^(j), t_(e)] would be based on the scheduledtemperature T_(sRTn) ⁰. In this case, only the portion of the productcold spot time-temperature profile over the time interval (t_(d), t_(r)]would be based on the portion of the actual retort time-temperatureprofile T_(aRTn)(t) over this time interval. In either case, thisresults in the actual lethality F_(i) ^(j) delivered over the timeinterval [t_(f,i), t_(r)] being computed more conservatively in steps142 and 148 of FIG. 3 and in sub-steps 161 to 168 of FIG. 7.

[0112] Similarly, the actual initial product temperatureT_(aIP)(t_(f,i)) for a container i was used in steps 142 and 148 of FIG.3 and in sub-steps 161 to 168 of FIG. 7 of FIG. 7 for computing theactual lethality F_(i) ^(j) over [t_(f,i), t_(r)]. However, rather thanusing this actual initial product temperature, the scheduled initialproduct temperature T_(sIP) may be used. This also results in the actuallethality being more conservative.

[0113] 2.d. More Aggressive Approaches

[0114] A more aggressive approach than that described earlier in section1.c. can be taken for defining the initially scheduled reel speed v_(s)⁰. In this approach, a first additional step could be added after step159 of FIG. 6 to determine whether the predicted total lethality F_(i) ⁰over [0, Δt₁ ⁰+ . . . +Δt₄ ⁰] is within the target total lethalityF_(targ) by a predefined lethality tolerance ΔF. If this is the case,the reel speed obtained in step 160 in the last iteration is used as theinitially scheduled reel speed. However, if this is not the case, thenthe reel speed from the last iteration is overly conservative. As aresult, a second additional step may be added to increase this reelspeed by, for example, 0.5Δv. Steps 151 to 159 and the two additionalsteps are then repeated until the first additional step is satisfied. Inthis way, the initially scheduled reel speed is further refined in anaggressive manner.

[0115] Similarly, a more aggressive approach can also be taken fordefining the re-scheduled reel speed v_(s) ^(j). In this case, the steps178 to 188 of FIG. 9 discussed in section 1.f. would also include thetwo additional steps just described.

[0116] 2.e. Deviations in Scheduled Initial Product Temperature and/orReel Speed

[0117] In addition to temperature deviations in the scheduled retorttemperatures T_(sRT1) ⁰, . . . , T_(sRT5) ⁰, there may be deviations inother scheduled parameters of the rotary sterilization process. Forexample, there may be deviations in the scheduled initial producttemperature T_(sIP) and/or the currently scheduled reel speed v_(s)^(j). Thus, the controller 104 may be configured to handle thesedeviations as well in order to identify any under and/or over processedcontainers { . . . , i, . . . }_(underpr) and/or { . . . , i, . . .}_(overpr) resulting from the deviation. This is done in a similarmanner to that described earlier in sections 1.b. to 1.e. fortemperature deviations in the scheduled retort temperatures.

[0118] 2.d. More Aggressive Approaches

[0119] A more aggressive approach than that described earlier in section1.c. can be taken for defining the initially scheduled reel speed v_(s)⁰. In this approach, a first additional step could be added after step159 of FIG. 6 to determine whether the predicted total lethality F_(i) ⁰over [0, Δt₁ ⁰+ . . . +Δt₄ ⁰] is within the target total lethalityF_(targ) by a predefined lethality tolerance ΔF. If this is the case,the reel speed obtained in step 160 in the last iteration is used as theinitially scheduled reel speed. However, if this is not the case, thenthe reel speed from the last iteration is overly conservative. As aresult, a second additional step may be added to increase this reelspeed by 0.5Δv. Steps 151 to 159 and the two additional steps are thenrepeated until the first additional step is satisfied. In this way, theinitially scheduled reel speed is further refined in an aggressivemanner.

[0120] Similarly, a more aggressive approach can also be taken fordefining the re-scheduled reel speed v_(s) ^(j). In this case, the steps178 to 188 of FIG. 9 discussed in section 1.f would also include the twoadditional steps just described. However, another additional step wouldalso have to be added.

[0121] 2.e. Deviations in Scheduled Initial Product Temperature and/orReel Speed

[0122] In addition to temperature deviations in the scheduled retorttemperatures T_(sRT1) ⁰, . . . , T_(sRT4) ⁰, there may be deviations inother scheduled parameters of the hydrostatic sterilization process. Forexample, there may be deviations in the scheduled initial producttemperature T_(sIP) and/or the currently scheduled reel speed v_(s)^(j). These deviations would be detected by monitoring the actualinitial product time-temperature profile T_(aIP)(t) and the actual reeltime-speed profile v_(a)(t)^(j). Thus, the controller 104 may beconfigured to handle these deviations as well in order to identify andsegregate any under and/or over processed containers { . . . , i, . . .}_(underpr) and/or { . . . , i, . . . }_(overpr) resulting from thedeviation. This is done in a similar manner to that described earlier insections 1.b. to 1.e. for temperature deviations in the scheduled retorttemperatures.

[0123] 2.f. Different Combinations of Cooling and Cooking Shells andTemperature Zones

[0124] The rotary sterilizer 102 of FIG. 1 was described as having onecooking shell 106-1 with three temperature zones 115-1, . . . , 3 andone cooling shell 106-2 with two temperature zones 115-4 and 5.Correspondingly, the flow and timing diagrams of FIGS. 3 to 9 weredescribed in this context as well. However, those skilled in the artwill recognize that the rotary sterilizer may have more than one cookingshell and more than one cooling shell with more or less temperaturezones. For example, in a simple case, the cooking and cooling shells mayeach have just one uniform temperature zone. As those skilled in the artwill recognize, the flow and timing diagrams of FIGS. 3 to 9 would haveto be correspondingly adjusted for the specific combination of cookingand cooling shells and temperature zones used.

[0125] 2.g. Other Continuous Source Sterilization Systems

[0126] The present invention has been described in the context of arotary sterilization system 100. However, as those skilled in the artwill recognize, the invention can be similarly practiced in any othercontinuous source sterilization system in which containers or carriersof containers are conveyed in line through the system's sterilizer. Forexample, the invention may be used in a hydrostatic sterilizer, asdescribed in concurrently filed and co-pending U.S. Pat. applicationSer. No. 09/______, entitled Controller and Method for Administering andProviding On-Line Handling of Deviations in a Hydrostatic SterilizationProcess, filed on Nov. 6, 1998, with Weng, Z. as named inventor. Thispatent application is hereby explicitly incorporated by reference.

[0127] 3. Conclusion

[0128] While the present invention has been described with reference toa few specific embodiments, the description is illustrative of theinvention and is not to be construed as limiting the invention. Variousmodifications may occur to those skilled in the art without departingfrom the true spirit and scope of the invention as defined by theappended claims.

What is claimed is:
 1. A method of administering a sterilization processbeing performed by a rotary sterilizer on a continuous line ofcontainers, the method comprising the steps of: controlling the rotarysterilizer to perform the rotary sterilization process according toscheduled parameters; and when a deviation in a specific one of thescheduled parameters occurs, identifying those of the containers thatwill in response have a total lethality predicted to be delivered tothem during the sterilization process that is less than a predefinedtarget lethality.
 2. The method of claim 1 wherein the specific one ofthe scheduled parameters is one of the group consisting of (1) ascheduled retort temperature in a temperature zone of the rotarysterilizer through which the line of containers is conveyed, (2) ascheduled initial product temperature for the containers, and (3) ascheduled reel speed for conveying the containers in line through therotary sterilizer.
 3. The method of claim 1 further comprising the stepof: compiling an actual retort time temperature profile for atemperature zone of the rotary sterilizer; and wherein the identifyingstep comprises the steps of: selecting at least some of the containersthat are effected by the deviation; for each of the selected containersthat has been conveyed into the temperature zone during the deviation,simulating a product cold spot time-temperature profile for thecontainer based on the actual retort temperature profile; computing thetotal lethality predicted to be delivered to the container during thesterilization process based on the product cold spot time-temperatureprofile; and determining whether the total lethality predicted to bedelivered to the container satisfies the target lethality.
 4. The methodof claim 3 wherein the simulating step uses a finite differencesimulation model to simulate the product cold spot time-temperatureprofile.
 5. The method of claim 4 wherein the total lethality is the sumof (1) a lethality actually delivered over a first time interval fromwhen the container is loaded into the rotary sterilizer to a currentsample real time, and (2) a lethality predicted to be delivered over asecond time interval from the current sample real time to when thecontainer is unloaded from the rotary sterilizer.
 6. The method of claim5 wherein: the lethality actually delivered over the first time intervalis based on the portion of the product cold spot time-temperatureprofile over the first time interval; the portion of the product coldspot time-temperature profile over the first time interval is based onat least a portion of the actual retort temperature profile over a timeinterval from a time when the container is first affected by thedeviation to the current sample real time.
 7. The method of claim 6wherein: the lethality predicted to be delivered over the second timeinterval is based on the portion of the product cold spottime-temperature profile over the second time interval; the scheduledparameters include one or more scheduled retort temperatures that arescheduled for the sterilization process in the second time interval; andthe portion of the product cold spot time-temperature profile over thesecond time interval is based on the one or more scheduled retorttemperatures.
 8. A controller for administering a sterilization processperformed by a rotary sterilizer on a continuous line of containers ofcontainers, the controller comprising: control circuitry configured tocontrol the rotary sterilizer; a memory configured to store a processcontrol program and a deviation program, the process control programbeing programmed to cause the control circuitry to control the rotarysterilizer in performing the sterilization process according toscheduled parameters, the deviation programmed being programmed toidentify, when a deviation in a specific one of the scheduled parametersoccurs, those of the containers that will in response have a totallethality predicted to be delivered to them during the sterilizationprocess that is less than a predefined target lethality; and amicroprocessor coupled to the memory and the control circuitry andconfigured to execute the process control and temperature deviationprograms.
 9. The controller of claim 8 wherein the specific one of thescheduled parameters is one of the group consisting of (1) a scheduledretort temperature in a temperature zone of the rotary sterilizerthrough which the line of containers is conveyed, (2) a scheduledinitial product temperature for the containers, and (3) a scheduled reelspeed for conveying the containers in line through the rotarysterilizer.
 10. The controller of claim 8 wherein: the process controlprogram is further programmed to compile an actual retort timetemperature profile for a temperature zone of the rotary sterilizer; andthe deviation program is programmed to identify the identifiedcontainers by: selecting at least some of the containers that areeffected by the deviation; for each of the selected containers that hasbeen conveyed into the temperature zone during the deviation, simulatinga product cold spot time-temperature profile for the container based onthe actual retort temperature profile; computing the total lethalitypredicted to be delivered to the container during the sterilizationprocess based on the product cold spot time-temperature profile; anddetermining whether the total lethality predicted to be delivered to thecontainer satisfies the target lethality.
 11. The controller of claim 10wherein the deviation program is programmed to use a finite differencesimulation model to simulate the product cold spot time-temperatureprofile.
 12. The controller of claim 10 wherein the total lethality isthe sum of (1) a lethality actually delivered over a first time intervalfrom when the container is loaded into the rotary sterilizer to acurrent sample real time, and (2) a lethality predicted to be deliveredover a second time interval from the current sample real time to whenthe container is unloaded from the rotary sterilizer.
 13. The controllerof claim 12 wherein: the lethality actually delivered over the firsttime interval is based on the portion of the product cold spottime-temperature profile over the first time interval; the portion ofthe product cold spot time-temperature profile over the first timeinterval is based on at least a portion of the actual retort temperatureprofile over a time interval from a time when the container is firstaffected by the deviation to the current sample real time.
 14. Thecontroller of claim 13 wherein: the lethality predicted to be deliveredover the second time interval is based on the portion of the productcold spot time-temperature profile over the second time interval; thescheduled parameters include one or more scheduled retort temperaturesthat are scheduled for the sterilization process in the second timeinterval; and the portion of the product cold spot time-temperatureprofile over the second time interval is based on the one or morescheduled retort temperatures.
 15. A rotary sterilization systemcomprising: a rotary sterilizer configured to perform a sterilizationprocess on a continuous line of containers; a controller configured to:control the rotary sterilizer in performing the rotary sterilizationprocess according to scheduled parameters; when a deviation in aspecific one of the scheduled parameters occurs, identify those of thecontainers that will in response have a total lethality predicted to bedelivered to them during the sterilization process that is less than apredefined target lethality.
 16. The rotary sterilization system ofclaim 15 wherein the specific one of the scheduled parameters is one ofthe group consisting of (1) a scheduled retort temperature in atemperature zone of the rotary sterilizer through which the line ofcontainers is conveyed, (2) a scheduled initial product temperature forthe containers, and (3) a scheduled reel speed for conveying thecontainers in line through the rotary sterilizer.
 17. The rotarysterilization system of claim 15 further comprising: a sensor to senseactual retort temperatures in a temperature zone of the rotarysterilizer; the controller is further configured to: compile an actualretort time temperature profile from the sensed actual retorttemperatures; and identify the identified containers by: selecting atleast some of the containers that are effected by the deviation; foreach of the selected containers that have been conveyed into thetemperature zone during the deviation, simulating a product cold spottime-temperature profile for the container based on the actual retorttemperature profile; computing the total lethality predicted to bedelivered to the container during the sterilization process based on theproduct cold spot time-temperature profile; and determining whether thetotal lethality predicted to be delivered to the container satisfies thetarget lethality.
 18. The rotary sterilization system of claim 17wherein the controller is still further configured to use a finitedifference simulation model to simulate the product cold spottime-temperature profile.
 19. The rotary sterilization system of claim17 wherein the total lethality is the sum of (1) a lethality actuallydelivered over a first time interval from when the container is loadedinto the rotary sterilizer to a current sample real time, and (2) alethality predicted to be delivered over a second time interval from thecurrent sample real time to when the container is unloaded from therotary sterilizer.
 20. The rotary sterilization system of claim 19wherein: the lethality actually delivered over the first time intervalis based on the portion of the product cold spot time-temperatureprofile over the first time interval; the portion of the product coldspot time-temperature profile over the first time interval is based onat least a portion of the actual retort temperature profile over a timeinterval from a time when the container is first affected by thedeviation to the current sample real time.
 21. The rotary sterilizationsystem of claim 26 wherein: the lethality predicted to be delivered overthe second time interval is based on the portion of the product coldspot time-temperature profile over the second time interval; thescheduled parameters include one or more scheduled retort temperaturesthat are scheduled for the sterilization process in the second timeinterval; and the portion of the product cold spot time-temperatureprofile over the second time interval is based on the one or morescheduled retort temperatures.